Domino-style earthquakes along blind normal faults in Northern Thessaly (Greece): kinematic evidence from field observations, seismology, SAR interferometry and GNSS

Autor: A. Karakonstantis, Sotiris Valkaniotis, Efthimios Sokos, Pierre Briole, A. Serpetsidaki, Athanassios Ganas, Ioannis Kassaras, Panagiotis Papadimitriou, Vasilis Sarhosis, Emmanouela Konstantakopoulou, Panagiotis Elias, Ioannis Karamitros, V. Kapetanidis, Varvara Tsironi, George Papathanassiou, Ilektra Karasante
Přispěvatelé: Laboratoire de géologie de l'ENS (LGENS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)
Jazyk: angličtina
Rok vydání: 2021
Předmět:
Zdroj: Bulletin of the Geological Society of Greece
Bulletin of the Geological Society of Greece, Ellēnikē Geōlogikē Etaireia, 2021, 58, pp.37. ⟨10.12681/bgsg.27102⟩
Δελτίο της Ελληνικής Γεωλογικής Εταιρείας; Τόμ. 58 (2021): Special Issue on the 2021 Northern Thessaly, Greece, Earthquake Sequence; 37-86
Bulletin of the Geological Society of Greece; Vol. 58 (2021): Special Issue on the 2021 Northern Thessaly, Greece, Earthquake Sequence; 37-86
ISSN: 0438-9557
2529-1718
DOI: 10.12681/bgsg.27102⟩
Popis: International audience; Here we present a joint analysis of the geodetic, seismological and geological data of the March 2021 Northern Thessaly seismic sequence, that were gathered and processed as of April 30, 2021. First, we relocated seismicity data from regional and local networks and inferred the dip-direction (NE) and dip-angle (38°) of the March 3, 2021 rupture plane. Furthermore, we used ascending and descending SAR images acquired by the Sentinel-1 satellites to map the co-seismic displacement field. Our results indicate that the March 3, 2021 Mw=6.3 rupture occurred on a NE-dipping, 39° normal fault located between the villages Zarko (Trikala) and Damasi (Larissa). The event of March 4, 2021 occurred northwest of Damasi, along a fault oriented WNW-ESE and produced less deformation than the event of the previous day. The third event occurred on March 12, 2021 along a south-dipping normal fault. We computed 22 focal mechanisms of aftershocks with M≥4.0 using P-wave first motion polarities. Nearly all focal mechanisms exhibit normal kinematics or have a dominant normal dip-slip component. The use of InSAR was crucial to differentiate the ground deformation between the ruptures. The majority of deformation occurs in the vertical component, with a maximum of 0.39 m of subsidence over the Mw=6.3 rupture plane, south and west of Damasi. A total amount of 0.3 m horizontal displacement (E-W) was measured. We also used GNSS data (at 30-s sampling interval) from twelve permanent stations near the epicentres to obtain 3D seismic offsets of station positions. Only the first event produces significant displacement at the GNSS stations (as predicted by the fault models, themselves very well constrained by InSAR). We calculated several post-seismic interferograms, yet we have observed that there is almost no post-seismic deformation, except in the footwall area (Zarkos mountain). This post-seismic deformation is below the 7 mm level (quarter of a fringe) in the near field and below the 1 mm level at the GNSS sites. The cascading activation of the three events in a SE to NW direction points to a pattern of domino-style earthquakes, along neighbouring fault segments. The kinematics of the ruptures point to a counter-clockwise change in the extension direction of the upper crust (from NE-SW near Damasi to N-S towards northwest, near Verdikoussa).
Databáze: OpenAIRE
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